Rotary compressor



Jan. 15, 1963 w. BAILEY ROTARY COMPRESSOR Filed April 26, 1960 4 Sheets-Sheet 1 a a; 0M M A 4 Sheets-Sheet 2 Filed April 26, 1960 Jan. 15, 1963 w. BAILEY ROTARY COMPRESSOR 4 Sheets-Sheet 3 Filed April 26, 1960 wwi m b? Q? 0 R ww B ArryJ:

1963 w. BAILEY 3,073,513

ROTARY COMPRESSOR I Filed April 26, 1960 4 Sheets-Sheet 4 application.

United States Patent cc 3,073,513 ROTARY COMPRESSOR Wilfred Bailey, Glasgow, Scotland, assignor, by mesne assignments, to Svenska Rotor Maskiner Aktiebolag, Naclra, Sweden, a corporation of Sweden Filed Apr. 26, 1960, Ser. No. 24,803 4 Claims. (Cl. 230-143) This invention relates to rotary compressors of the positive displacement type including two or more rotors disposed within a housing and formed with interengaging helical lobes and grooves, which, however, are not in physical contact with one another, but engage with small clearances. correspondingly. the rotors do not contact the housing'but rotate with small clearances between the lobe 'tips and the inner surface of said housing which is provided with a discharge port proportioned to cause the pressure of the gas being compressed to be raised ithin the compressor before the gas is discharged. The compressor has a working chamber into which a liquid is injected to seal the clearances between the rotors and between the rotors ,and casing, and to cool the gas being compressed.

The present invention is an improvement in or modifidation of that formingthe subject of my prior copending application Serial Number 696,349, filed November 14, 1957, now abandoned, of which this application is a continuation-in-part.

The invention herein has for its chief object to' provide a compressor of a more simplified andcompact construction than that disclosed in the aforesaid prior copendin A further object is to provide a rotary compressor of the, type referred to above in which a liquid is introduced into the compressor in sufiicient amounts'to seal the small clearances and also to enableone rotor which is' driven from an external source to drive the other or others without the necessity for the usual intermeshing timing gears hitherto employed. The liquid may be a-lubri'cating oil or any other suitable liquid having the necessary lubricating qualities. p

In order that the nature of the invention may be clearly understood and readily carried into effect the same will be hereinafter more fully described with reference to FIG. 6 is a section along the line -vi vi of FIG, 5.

FIG. 7 is a section through the working chamber along the line Vii-VII of FIG. 5. c c I Referring now to FIGS. 1 and,2, 10. denotes a rotary compressor of the positive displacement type having two or more rotors disposed. within an outer casing and formed with interengaging.helicallobes and grooves engaging with smallclearances ashereinafter described .with

reference toFIG. 3.- As is well known in the operationjof such a compressor air or gas entering by way of an inlet duct ll is compressedand thereafter discharged through an outletductlZ. One of the rotorsis driven through a driving shaft 13v and serve sto'drivetlie other frotor'which carries on its shaft 14 two pumps ,15 andlo, the purpose of which will be hereinaft er described. .Itmay 'be mentioned here that while hitherto the ,drive fromone rotor to the other has been effected by means ofintermeshing f timing gears the arrangement according to the invention is such that such gears will be rendered unnecessary and the rotor driven by the shaft 13 will be effective directly to drive the other rotor or rotors.

In the embodiment shown in FIG. 1 the arrangement is such that a liquid such as an oil or other liquid havingv the necessary lubricating qualities is introduced into the compressor casing. The liquid acts as a sealing medium for the clearances between the interengaging lobes and grooves of the rotors, as a coolant for the air or gas being compressed and also as a lubricant for the anti-friction bearings supporting the rotors. Referring now specifically to FIG. 1, 1'7 denotes a pressurized tank from which oil is fed both to the interior of the compressor casing to act as a sealing medium and also as a coolant and also to the rotor bearings. The pump 16 on the shaft 14 is adapted on operation of the compressor to draw oil from the tank 17 through a pipe 18 and to deliver such oil via a pipe 19, cooler'20 and pipe 21 into the compressor casing adjacent the air inlet where it enters the clearances between the rotors and between the rotors and the casing and also enters the rotor bearings.

The majority of the oil thus supplied to the compressor is discharged with the compressed air or gas, after acting as a sealing and cooling medium, through the duct 12 and hence to a separator 22 wherein the oil is separated from the air or gas and returns through a pipe 23 to the tank 17, the compressed air or gas being discharged through a conduit 24.

A proportion of the oil passing to the bearings at the inlet and outlet ends ofthe rotors will drain from such bearings through ducts 25 and 26 and it will be returned by the pump 15 on the shaft 14 via the duct 27 to the compressor for repassage through the latter.

Although in the foregoing the arrangement is such that the rotor bearings are pressure fed with lubricant it would nevertheless be possible to employ splash lubrication 1 from the injection.

In Fl'G. 2 is shown a diagrammatic arrangement of a system wherein the sealing and cooling medium is a liquid other than the lubricant for the rotor hearings. in this case the sealing and cooling medium is contained in a pressurized tank 17 and similarly to the arrangement in FIG. 1 is supplied by the pump 16 through pipe 19, 'cooler 26 and pipe 21 to the interior of the compressor.- The liquid discharged with the compressed'air or gas through the duct; 32 is delivered as before to the septa-- rator 22 and after separation returns via pipe 23 to the 1 The lubricating system comprise a ventilated-tank 28 from which oil is supplied by the pump 1S'through a pipe 29', acooler 3t? and a pipe 31 to the outlet end bearingsand through abranch'pipe 32 to theinlet end bearings. Oil draining from these two bearings passes through pipes 33 and 34 back to the tanklh.

It will be appreciated that with an arrangement such as 1 into the working chamberot the compressor is permitted to pass to such hearings to provide for lubrication and The amount of liquid injected ber of the compressor'will depend on the'cha'r'acteris'tic ofthe compressor. for example tests have shown that the volumetric r'aito between the liquid introduced for example in the formbf oil has varied between 0.24%

liquid to at maximum speedand.l.1% liquid to gas cooling thereof, theresultant construction will be simpler sincethere is no necessityfor external oradditional :lub-

rication supplies such, for example, as isthecase with th arrangement shown in F1G. v I p I 3,073,513 Patented Jan. 15, 1963 tank 17, the air or gas being discharged through the pipe is shown in FIG. I wherein the rotors are supported inf iantifrictionbearings and a portion of the liquid injected into the working chan l low speed of the compressor, these figures being given merely by way of example only and without limitation thereto. These volumetric ratios correspond to mass ratios of liquid to gas of 1.5/1 and 10/ l. The optimum or preferred mass ratio appears to be about 4/ i at maximum compressor speed.

The viscosity of the oil or other medium employed will depend on the clearances between the lobes of the rotors and the smaller the clearance the thinner the oil or other medium which may be used. The clearance will vary with the rotor diameter but not however in direct proportion and the clearances employed in practice will be a compromise between what is desirable and what is possible in production. Purely as examples only the clearances used between the rotor lobes, measured on the end face may be .0024-.O04" in the case of 5" diameter rotors and 0035-006 in the case of 8 diameter rotors. It is to be understood that due to the smaller temperature rise obtained when using liquid as a sealing medium and coolant, the clearances between the rotors and between the latter and the housing, may initially be made smaller without fear of rubbing contact on expansion, due to temperature, than in the case of dry air machines. However, the outlet end clearance, that is, the clearance between the rotors and the housing at the high pressure delivery end, is believed to be of considerable importance, and in order to limit leakage across the high pressure ends of the rotors, the clearance between the rotors and the housing should not exceed 0.010 inch. In general higher viscosity oil decreases the back leakages giving greater volumetric efficiency but increased churning loss. For rotors less accurately produced, i.e. with larger local clearances for the same backlash it would be preferable to use higher viscosity oil.

Since the rotational speed of a compressor varies with the size of the machine, a governing factor in obtaining good results will be the tip speed which should be approximately constant for all sizes of machines. Tests have shown that satisfactory results are obtained with tip speeds of between 60 and 145 feet per second.

FIGS. 3 to 7 show a preferred construction of the compressor according to the invention. The compressor illustrated is intended to form a portable compressor unit with a diesel or other internal combustion engine. The engine shaft 35 carries a flywheel 36 enclosed within a flywheel housing 37 and carrying an externally toothed gear 33. The compressor includes a main casing comprising parts 39, 40, the part 39 being bolted to the flywheel housing 37.

The casing part 39 supports the rotor bearings at the inlet end of the compressor and forms a housing for the speed increasing gears of the rotors. The casing part 40 is formed with the bottom half of the main rotor bores 75, 76 and supports the rotor hearing at the outlet end of the compressor. To the casing parts are secured an inlet casing member 56 formed with an inlet duct 77 through which the gas passes to the rotors and an upper casing member 57 formed with the top half of the rotor bores 75, 76 and with a suitably shaped delivery port 78 (see FIGS. 4 and 7). The upper casing members 56, 57 will be rigidly fixed to the lower casing para 39, 40 by means of a number of threaded studs 58 passing through aligned holes 42 in flanges on the respective parts.

Two rotors 43, 44 are located in the bores 75, 76 of the casing and are carried by suitable bearings. At the inlet end the bearings comprise main bearings 45 which in the illustrated construction are of thewhite metal half shell 5 type but may-if desired be anti-friction bearings of the ball and roller type. ,Similar bearings 46 are-located at the outlet end of the compressor and in addiiton thrust bearings 47 of the tilting pad type are provided at this end. .Alternatively ball or roller bearings of the axial thrust type may replace the bearings 46, 47. Labyrinth seals 48 are fitted at both ends of the rotors.

The male rotor 43 is fitted with an overhung pinion 49 forming part of the speed increasing gear and, on application of the casing part 39 to the flywheel housing 37, mating directly with the gear 38 secured to the flywheel. Thus the male rotor 43 is driven from the engine and as indicated above by virtue of the introduction of the liquid into the working chamber of the compressor said rotor 43 is effective to drive the female rotor 44 without the necessity for any intermeshing timing gears such as have hitherto been employed. It may be pointed out here that the mounting of the rotors is such that the small clearances between the lobes 50, 51 of the respective rotors will be maintained without possibility of direct contact of said lobes.

Located outside the compressor casing and mounted on the end plate 52 and driven by the shaft of the female rotor 44 are the pumps, denoted diagrammatically at 53, for injecting the liquid sealing and cooling medium into the compressor casing and for supplying lubricant to the end bearings of the rotors.

From the above description it will be understood that the rotors 43, 44 are mounted within a casing which is divided longitudinally along the diametrical plane of the rotors. This enables the rotors to be inspected on removal of the upper casing parts and to be withdrawn from the casing without drawing the same axially through the casing after removal of the end plate 52 of the casing.

In operation the driving members 35, 36 drive the male rotor 43 through the intermediary of the meshing gears 38, 49 and air enters the compressor through the air inlet duct 77 and through the inlet port 82 (FIG. 6) at the inlet end of the easing into the working chamber 83 formed by the bores 75, 76 of the casing and the end walls 84, 85 thereof. The air in the working chamber passes into the grooves 86, 87 of the intermeshing rotors 43, 44 and is compressed therein by the progressive engagement of the rotor lobes within said grooves and is moved to the outlet end of the working chamber to exhaust through the compressed air outlet port 78. During rotation of the rotors 43, 44 the pump 72 on the shaft of the female rotor 44 draws the sealing and cooling medium from a supply of, for example, lubricant (not shown in FIGS. 3-7) and delivers said medium to the apertures 81 where it enters the grooves 86, 87 of the rotors and seals the clearances 80 between the intermeshing elements of the rotors and also seals the clearance shown diagrammatically in FIG. 7 at 88 between the rotor lobes 70, 71 and the walls of the bores 75, 76. Said medium passes through the outlet port 78, together with the compressed air or other gaseous medium and is separated from the compressed air outside the compressor in the manner described with reference to FIG. 1 or FIG. 2.

Rotary compressors of the kind described above are normally designed for an optimum built-in presure ratio ,which means that the outlet port of the compressor has a definite predetermined shape normally substantially triangular as shown in FIG. 4, and the delivery starts at a predetermined distance along the rotor axis. The nearer the location of the point of opening 90 (apex) of the triangularly shaped outlet port 78 to the delivery end of the machine, the higher will be the pressure ratio. In determining the pressure ratio of machines having liquid introduced into the gas inlet, this would appear to differ slightly from the theoretical location for machines using dry air. For example, in obtaining an outlet pressure of lbs. per square inch corresponding to a pressure ratio of 7.8/1, a built-inpressure ratio of between 7.0/1 and 9.0/1 depending on the speed of the rotors gifes'optimum results when oil is introduced into the gas inet.-

While in the above description reference has been made to compressors forming part of a portable compressor 'unitdriven by a diesel engine, it is to be understood that a compressor constructed and operating according to'this invention may, if desired, be installed in a stationary plant driven by an electric motor running at speeds of the order of 1500 r.p.m. or by any other suitable power source.

Various changes and modifications may be made without departing from the spirit and scope of the present invention and it is intended that such obvious changes and modifications be embraced by the annexed claims.

What I claim is:

1. A rotary compressor comprising a casing having a working chamber extending longitudinally in said casing and formed of a pair of intersecting bores, said casing having an inlet port communicating with one end of said chamber, said casing having an outlet port providing a discharge from said chamber, a male rotor positioned in one of said bores, a female rotor positioned in the other of said bores, said male rotor having spiral lobes, said female rotor having spiral grooves each receiving in slightly spaced intermeshing relation one of said lobes, said rotors being slightly spaced from the walls of their respective bores, and separate means operable upon operation of the compressor for supplying a lubricating and cooling fluid to said chamber to fill the spaces between said lobes and the walls of said grooves, said fluid disposed in the space between said lobes and the walls of said grooves constituting the sole means for transmitting driving force from one rotor to the other.

2. A rotary compressor as defined in claim 1 wherein a pump is provided for said fluid, and wherein said female rotor is provided with a forwardly extending pump shaft extending through said casing and connected to said pump.

3. A rotary compressor as defined in claim 1 wherein a drive shaft is provided for said compressor, a toothed flywheel is affixed to said drive shaft, a pinion shaft extends from said male rotor rearwardly through said casing, and

a pinion is aflixed to said pinion shaft exteriorly of said casing and engaged with the teeth of said flywheel.

4. A rotary compressor as defined in claim 1 wherein a pump is provided for said fluid, and wherein said female rotor is provided with a forwardly extending pump shaft extending through said casing and connected to said pump, wherein a drive shaft is provided for said compressor, a toothed fiywheel is afiixed to said drive shaft, a pinion shaft extends from said male rotor rearwardly through said casing, and a pinion is affixed to said pinion shaft exteriorly of said casing and engaged with the teeth of said flywheel. 1

References Cited in the file of this patent UNITED STATES PATENTS 1,319,776 Kerr Oct. 28, 1919 1,409,868 .Kien Mar. 14, 1922 1,672,571 Leonard June 5, 1928 1,673,260 Meston et al. June 12, 1928 1,673,262 Meston et al. June 12, 1928 1,675,524 Zajac July 3, 1928 1,930,403 DeBije Oct. 10, 1933 2,243,874 Lysholm June 3, 1941 2,361,146 Montelius Oct. 24, 1944 2,477,002 Paget July 26, 1949 2,627,161 Lindhagen et a1. Feb. 3, 1953 2,847,157 Nilsson Aug. 12, 1958 2,905,376 Davey Sept. 22, 1959 FOREIGN PATENTS 16,476 Great Britain of 1895 220,581 Australia Feb. 25, 1959 540,444 Germany Dec. 15, 1931 

1. A ROTARY COMPRESSOR COMPRISING A CASING HAVING A WORKING CHAMBER EXTENDING LONGITUDINALLY IN SAID CASING AND FORMED OF A PAIR OF INTERSECTING BORES, SAID CASING HAVING AN INLET PORT COMMUNICATING WITH ONE END OF SAID CHAMBER, SAID CASING HAVING AN OUTLET PORT PROVIDING A DISCHARGE FROM SAID CHAMBER, A MALE ROTOR POSITIONED IN ONE OF SAID BORES, A FEMALE ROTOR POSITIONED IN THE OTHER OF SAID BORES, SAID MALE ROTOR HAVING SPIRAL LOBES, SAID FEMALE ROTOR HAVING SPIRAL GROOVES EACH RECEIVING IN SLIGHTLY SPACED INTERMESHING RELATION ONE OF SAID LOBES, SAID ROTORS BEING SLIGHTLY SPACED FROM THE WALLS OF THEIR RESPECTIVE BORES, AND SEPARATE MEANS OPERABLE UPON OPERATION OF THE COMPRESSOR FOR SUPPLYING A LUBRICATING AND COOLING FLUID TO SAID CHAMBER TO FILL THE SPACES BETWEEN SAID LOBES AND THE WALLS OF SAID GROOVES, SAID FLUID DISPOSED IN THE SPACE BETWEEN SAID LOBES AND THE WALLS OF SAID GROOVES 